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Raumfahrt - JAXA´s Asteroid Explorer Hayabusa-2 bei Asteroid 1999 JU3 -Update-9

17.01.2019

Hayabusa2 team sets date for sample collection, considers two touchdown sites

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Japan's Hayabusa2 spacecraft will try to collect a sample from asteroid Ryugu during the week of 18 February, mission officials said during a press briefing last week. Should problems arise, a backup week is available starting 4 March. The team is now considering two sample collection sites, the smaller of which is just a few meters across.

Hayabusa2 spent the end of 2018 looping a safe distance from asteroid Ryugu and back again during solar conjunction, returning to its home position 20 kilometers away on 29 December.

JAXA's website has some interesting details about how the team tried to communicate with—or at least, get some very basic information from—Hayabusa2 during solar conjunction. Computer data is binary, a stream of zeros and ones. Spacecraft transmit the zeros and ones by varying the intensity of the spacecraft's radio signal. Unfortunately, when a spacecraft is next to the Sun in the sky, plasma near the Sun's surface interferes with the signal, making the intensity fluctuate so badly some zeros look like ones and some ones look like zeros. To compensate for this, Hayabusa2 sent the same information multiple times. Engineers gave computer algorithms on Earth several copies of the same message, using them to sort out which parts of the signal were supposed to be zeros and which parts were supposed to be ones.

Now that Ryugu and the Sun aren't so close to each other in the sky, Hayabusa2 is back to normal operations, and that means preparing for touchdown and sample collection! The first touchdown is planned for the week of 18 February, with a backup the week of 4 March.

As a reminder, Ryugu is surprisingly rocky, and there are very few places to safely bring the spacecraft down to collect a sample. The team is still considering a circular, 20-meter-wide site called L08-B—more specifically, an irregular region within that called L08-B1—but they are also eyeballing another spot a few meters away called L08-E1.

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There are pros and cons to both sites. L08-B1 is 12 meters wide at its narrowest point, which gives Hayabusa2 plenty of margin (the spacecraft measures 6 meters wide across its solar panels). But despite being free of larger boulders, L08-B1 is scattered with rocks about 60 centimeters in size. The spacecraft's sampler horn is only a meter long.

L08-E1, on the other hand, has smaller rocks, under 60 centimeters in size. But here's the catch: at its narrowest point, the landing site is just 6 meters wide—the same size as the spacecraft. At first, I assumed this meant the spacecraft would have to turn 90 degrees to safely grab a sample from L08-E1, like a car pulling in to a parking space. However, in clarifying this with the team, I learned that isn't necessarily the case. The landing areas are simply where the sampler horn can touch; the entire spacecraft doesn't actually have to fit into those. The sampler horn sticks a meter down from the spacecraft, and then there's another 1.25 meter or so of spacecraft between the base of the horn and the solar panels.

The team also says that they can be confident of the spacecraft's position roughly within about 1 meter. Stop and think about that for a moment: Ryugu is 354 million kilometers from Earth. It takes radio signals, traveling at the speed of light, 20 minutes to travel that far. And Hayabusa2 can touch down on Ryugu with an accuracy of a single meter.

Another advantage of L08-E1 is that it's closer to the target marker the spacecraft dropped, just a few meters away, meaning Hayabusa2 can keep it in sight for longer as it descends to collect a sample. The team has decided not to drop another target marker, according to Makoto Yoshikawa, the Hayabusa2 project mission manager.

"Two target markers in the same area can cause trouble for the autonomous operation," he said in an email. "This is a risk. So we have decided not to use extra target makers."

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JAXA

RYUGU NAMED FEATURES
The names in yellow are all officially recognized by the International Astronomical Union, while the two in orange are unofficial. Trinitas and Alice’s Wonderland are nicknames of the MINERVA-II1 and MASCOT landing sites, respectively.

In other mission news, the team has released a map of named Ryugu surface features, with the theme of "children's stories." The names in yellow are all officially recognized by the International Astronomical Union; while the two in orange are unofficial.

Last week's press materials say the Hayabusa2 team submitted their proposal to use the children's-story theme for names to the IAU on 28 June 2018, the day after they arrived at Ryugu. A working group accepted the theme three months later, on 25 September. On 12 October, the team proposed 13 surface feature names along that theme. Nine of those names were accepted as proposed, and 4 were accepted after some further discussion with the IAU.

Perhaps the most notable outcome from these new names is that we can now officially call the giant boulder at Ryugu's south pole Otohime Saxum. "Saxum" is Latin for boulder, and Otohime is the name of an undersea princess connected to the story of Ryugu. That story, as I understand it, says that Ryugu was an underwater dragon palace. A fisherman named Urashima (a newly named Ryugu crater) traveled there on a turtle, where he received a treasure box (read: surface sample) from Otohime!

Here's a good image with Otohime Saxum in it. Note that here, it's at the top of Ryugu—most of the images released by JAXA before September had the south pole on top.

Quelle: The Planetary Society

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Update: 6.02.2019

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Hayabusa 2 probe to try to land on asteroid Ryugu on Feb. 22: JAXA

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TOKYO -- The Japan Aerospace Exploration Agency (JAXA) will try to land its Hayabusa 2 probe on the asteroid Ryugu on Feb. 22, the agency said on Feb. 6.

In its landing mission, Hayabusa 2 will use target markers it released earlier on the celestial object, and attempt to collect rocks and sand from the surface and bring them back to Earth.

JAXA postponed Hayabusa 2's scheduled landing in October last year due to the unexpectedly rocky surface conditions of the asteroid.

The Hayabusa 2 probe was launched on an H-IIA rocket from the Tanegashima Space Center in Kagoshima Prefecture, southern Japan, on Dec. 3, 2014, and is expected to leave the asteroid sometime around the end of 2019 and return to Earth in late 2020.

Quelle: The Mainichi

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Japan's Hayabusa2 probe to land on asteroid on Feb 22

A Japanese probe sent to examine an asteroid in order to shed light on the origins of the solar system is expected to land on the rock later this month, officials said Wednesday.

The Japan Aerospace Exploration Agency (JAXA) said the Hayabusa2 probe is expected to touch down on the Ryugu asteroid at 8am local time on February 22.

"The landing point is decided and how we're going to land is confirmed, so we want to do our best to achieve this without making mistakes," JAXA project manager Yuichi Tsuda told reporters.

The announcement comes after the agency in October delayed the touchdown for several months, saying they needed more time to prepare the landing as the latest data showed the asteroid's surface was more rugged than expected.

Scientists are already receiving data from other probes deployed on the surface of the asteroid.

In October, JAXA successfully landed a new 10-kilogramme (22-pound) observation robot known as MASCOT -- "Mobile Asteroid Surface Scout."

Loaded with sensors, the robot can take images at multiple wavelengths, investigate minerals with a microscope, gauge surface temperatures and measure magnetic fields.

Hayabusa2, about the size of a large fridge and equipped with solar panels, is the successor to JAXA's first asteroid explorer, Hayabusa, which is Japanese for falcon.

The Hayabusa2 mission, which costs around 30 billion yen ($260 million), was launched in December 2014 and will return to Earth with its samples in 2020.

Photos of Ryugu -- which means "Dragon Palace" in Japanese, a castle at the bottom of the ocean in an ancient Japanese tale -- show an asteroid shaped a bit like a spinning top with a rough surface.

By collecting samples from it, scientists hope to answer some fundamental questions about life and the universe, including whether elements from space helped give rise to life on Earth.

Quelle: France24

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★ Hayabusa2 status (week of 2019.1.7) ★

With solar conjunction and the New Year holiday now over, Hayabusa2 operations have ramped up this week. First was the tour operation. We moved to a region (so-called BOX-B) that is shifted slightly from the usual home position (so-called BOX-A) and conducted a series of scientific observations. By moving along the X-direction, we were able to acquire data with the Sun directly behind the spacecraft. Next was the vibration test for the sampler. The purpose was to confirm that Hayabusa2 will not perform an emergency escape if it incorrectly detects the vibration of the sampler before landing. Hayabusa2 was moved in the sequence of the final descent phase and acquired data on how the sampler vibrates. The final task was to do with the pressure that regulates the chemical propulsion system. In order to perform a ΔV test in the next week in preparation for the future SCI operation, we pre-adjusted the pressure of the fuel and oxidiser tanks to ensure standard values. “Let’s safely land!” Hayabusa2 is working hard to realise the hope of the New Year after a refreshing rest!

2019.1.16 O.M.

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★ Hayabusa2 status (week of 2019.1.14) ★

On 1/16, we conducted a prolonged injection test for the RCS (chemical thrusters) in preparation for the SCI (impactor) operation. After separating the impactor in the SCI operation, the spacecraft will swiftly hide behind the asteroid to avoid flying debris generated by the explosion. This involves a RCS thruster injection for about 20 seconds in the ±X and ±Z direction, during which time a translational force of several 10s N will be applied to the spacecraft. This test checked whether attitude control and the RCS subsystem functions worked as expected under a strong disturbance that is not usually experienced. Although the test was run for about half the final injection time, both the attitude control and RCS subsystem worked almost as expected and we acquired valuable data for the actual SCI operation. In addition, on 1/18 following the operation of the previous week, we tested the vibration of the sampler horn and gathered the remaining necessary data.

2019.1.21 Y.M.

★ Hayabusa2 status (week of 2019.1.21) ★

This week was the tour or “BOX-B” operation. Here, the spacecraft’s altitude is lowered from the Home Position (HP) by about 2km and shifted towards the north pole by about 9km. We moved slowly over several days, arriving on 1/24. In the previous BOX-B operation, we observed the south pole hemisphere of the asteroid, so this time we moved to observe the north pole region from above. We stayed at that location for about 1 day to make scientific observations, after which a ΔV (acceleration) was performed and we are now returning to the HP (schedule to arrive at HP on 1/31). Observations were made with all scientific instruments; ONC, TIR, NIRS3 and LIDAR. Working with both the Goldstone and Madrid ground stations, as well as Usuda, we were able to acquire the observational data over the weekend. We also gathered additional valuable data, including a health check for the ONC and dark imaging from the TIR during the tour.

2019.01.29 M.H.

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Locations on the surface of Ryugu
have been named!

Place names for locations on the surface of Ryugu were discussed by Division F (Planetary Systems and Bioastronomy) of the International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (hereafter IAU WG) and approved in December 2018. We will introduce the place names in this article and the background to their selection.

As the appearance of Ryugu gradually became clear during the approach phase in June 2018, we used nicknames amongst the Hayabsua2 Project team to distinguish regions of the terrain. (For example, the crater now named “Urashima” was referred to as the Death Star crater in Star Wars!) However, in order to introduce Ryugu to the world, it is necessary to have names that are intentionally recognized rather than nicknames, which can be referred to in scientific papers and other articles. Therefore, the discussion regarding naming the Ryugu surface topology began within the team.

To name a place on a celestial body in the Solar System, you must first decide on a theme. For example, the theme for places on Venus is the “names of goddesses”. During discussions between the domestic and overseas project members, suggestions such as “names of castles around the world”, “word for ‘dragon’ in different languages” and the “names of deep-sea creatures” were proposed for the place name theme on Ryugu. After an intense debate, the theme was selected to be “names that appear in stories for children” and a theme proposal was put to the IAU WG. The proposal was accepted on September 25, after which the discussion moved to selecting the topographical features to be named and the choice of name.

Names cannot be attributed to any location. Instead, there are restrictions on the places that can be assigned an official name involving considerations such as scientific importance or size on the celestial body. With this in mind, volunteers from the project members as well as planetary geology experts (hereinafter referred to as the Place Name Core Members ※1) discussed the place selection and completed the application forms for naming based on the exploration data. On October 12, we proposed 13 place names to the IAU WG. After additional discussion with the WG, 9 were accepted as proposed by the team and the remaining 4 names were approved after an amendment suggested by the IAU.

The surface of celestial bodies has a range of different topologies. We applied to give names to four different topology types on the Ryugu surface. The first type is “dorsum” which originates from the Latin for peak or ridge. The second type is “crater” which are familiar structures on the Moon and asteroids. Then “fossa” meaning grooves or trenches and finally the Latin word “saxum” for the rocks and boulders that are a main characteristic of the Ryugu terrain. Saxum is actually a new classification of terrain type that we applied to introduce due to the nature of Ryugu.

Numerous boulders are distributed on the surface of Ryugu. Regardless of where you look, there are rocks, rocks and more rocks. This is a major characteristic of Ryugu and continues to make plans for the touchdown operation of the spacecraft difficult. Additionally, spectroscopic observations revealed that the giant boulder (Otohime saxum) at the south pole has not only a substantial size, but also a distinct visible light spectrum that reveals materials and surface conditions that are different from the surrounding areas. Since this boulder is the most important topographical feature for understanding the formation history of Ryugu, the Project strongly hoped to name it. However, there was no precedent for boulder nomenclature and even the name type did not exist (during the exploration of the first Hayabusa mission, naming the huge boulder protruding from asteroid Itokawa was not allowed). We therefore proposed the type name for boulders at the same time as applying for the place names. Since terrain type names are usually Latin, we proposed “saxum” (meaning rocks and stones in Latin) as the type name for boulders. The IAU accepted this nomenclature for boulders with a few conditions (such as the boulder must be 1% or more of the diameter of the celestial body) and the type name that we suggested was adopted (!). This is how the new terrain type “saxum” was born.

Figure 1 shows a map of Ryugu with the place names labelled. Additionally, Figure 2 shows the location of the places on images of Ryugu taken from four different directions. In these figures, the north pole of Ryugu is at the image top. Please keep in mind that the north pole of Ryugu is in the same direction as the south pole on Earth, as Ryugu rotates in the opposite direction. Table 1 shows a list of the place names.

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Figure 1: Map of Ryugu showing the place names.
Trinitas and Alice’s Wonderland are nicknames of the MINERVA-II1 and MASCOT landing sites, respectively, and not place names recognized by the IAU. (Image credit:JAXA ※2)
(2019.02.04, Correction: In the original article, the MINERVA-II1 site name was given as “Trinitas” but has been corrected to “Tritonis”.)

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Figure 2: The location of place names on Ryugu.
Tritonis and Alice’s Wonderland are nicknames of the MINERVA-II1 and MASCOT landing sites, respectively, and not place names recognized by the IAU. (Image credit:JAXA ※2)
(2019.02.04, Correction: In the original article, the MINERVA-II1 site name was given as “Trinitas” but has been corrected to “Tritonis”.)

As it is difficult to get a feel for how the place names were chosen from just a list, we will introduce the story behind the main choices below.

The asteroid name “Ryugu” comes from the Japanese fairy tale of Taro Urashima. In the story, Urashima is a fisherman who rescues a sea turtle from the cruelty of a group of children. The turtle takes Urashima to the underwater palace of Ryugo-jo (Dragon Palace), where he meets the princess, Otohime. After 3 years, Urashima wishes to return home and is given a treasure box (tamatebako) by Otohime with instructions never to open it. But when Urashima returns to the surface, he discovers everything he knew has changed as 300 years has actually past. In confusion, Urashima opens the treasure box and is engulfed in white fog. When it clears, he has become an old man, as the box contained his age.

With the name of the asteroid being Ryugu, there was a strong desire from the Project to use other names that appear in Urashima’s story for major asteroid topography. However, place names cannot be common nouns so words such as “sea bream”, “flounder” and “turtle” do not work and we were limited to names such as Taro Urashima, Otohime etc.

Therefore, “Urashima” was chosen for the biggest crater on Ryugu and “Otohime” for the largest boulder near the south pole. Both of these are very important features for deciphering the formation history of Ryugu. However, Otohime had already been used! Venus (whose place theme uses the names of goddesses) had already a location named Otohime Tholus. Otohime was therefore initially refused by the IAU when it was proposed. But Otohime is an extremely important person in the story of Taro Urashima and how can we collect the tamatebako if Otohime is not on Ryugu?! (That was a joke, but we did want to use such a relevant name.) Since the name was important to the Project, the place name core members refined the proposal to the IAU, explaining why Otohime should be one of the main topological features on Ryugu and this was accepted.

A defining feature of Ryugu is that the shape is similar to a spinning top or abacus bead. This shape is the combination of two cones which appear almost circular when seen from the north pole. The ridge where they join was named “Ryujin”, after the ruler of the Dragon Palace who is the father of princess Otohime. This name came from the Place Name Core Members who felt the ridge resembled a dragon coiling around the asteroid or an ouroboros (the image of the serpent or dragon that swallows its own tail). (There was actually a similar illustration in the “Imagining Ryugu” art contest!)

On either side of Otohime saxum there are large grooves extending in the equatorial direction. In the story of Taro Urashima, Otohime lives in this mysterious place at the bottom of the ocean which is sometimes depicted as a different world in the various retellings of the tale. This world is often called “Horai”, “Tokoyo” or “Niraikanai”. The grooves adjacent to Otohime saxum were therefore named Horai fossa and Tokoyo fossa.

There is a reasonably big boulder to the southeast of the Urashima crater. According to one version of the tale, the place where Taro Urashima helped the turtle and left to travel to Ryugu-jo is the place “Ejima”, which gave the boulder its name Ejima saxum.

There are also large craters on both sides of Urashima crater. In particular, there are two craters stuck together along the north-south direction to the west. This state reminded us of the kibidango (Japanese dumplings) in another Japanese fairy tale called Momotaro. The northern crater of the pair was therefore named “Momotaro crater” and the southern crater became “Kibidango crater”. To the east of the Urashima crater, there is a crater with big black boulder inside. This reminded us of the Japanese tale of Kintaro, a boy with super strength who carried a broad-axe, and so was named “Kintaro crater”.

Ryugu also has topological names derived from children’s stories from outside Japan. For example, while you might not immediately recognize the name of the Cendrillion crater, the name is from the original French name for the familiar fairy tale, “Cinderella”. The name of the Brabo crater is derived from the name of the hero of a Netherlands tale, which was proposed by the overseas project members. The Kolobok crater and Catafo saxum were both names proposed by the IAU WG. They are taken from Russian and Cajun (famous for Cajun cuisine in the USA) folktales.

These are the place names formally recognized by the IAU WG. In addition, there are two nicknames shown in Figures 1 and 2; Trinitas (the MINERVA-II1 landing site and named for the goddess Minerva’s birth place) and Alice’s Wonderland (the MASCOT landing site). These were places named by the project to identify the points where MINERVA-II1 and MASCOT landed, but are not official names recognized by the IAU.

We are planning to review and propose place names from time to time as we continue to observe and research asteroid Ryugu. What kind of story should appear on Ryugu next?

Quelle: JAXA

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